lecture 4

Question 1

observational studies

Answer 1

observe the outcomes without intervening to affect them

Question 2

experimental studies

Answer 2

researcher manipulates the exposure (usually drug or tx) to compare to standard of care

Question 3

types of observational studies

Answer 3

cohort
case control
cross sectional

Question 4

cohort studies

Answer 4

subjects are selected based on exposure status

Question 5

prospective cohort study

Answer 5

compares disease prevalence in the exposed and unexposed

Question 6

retrospective cohort study

Answer 6

begin with exposure of interest and probe back for exposure info

Question 7

advantages of cohort studes

Answer 7

maintain temporary sequence

GOOD FOR RARE EXPOSURES, RAPIDLY FATAL DZ

can study multiple dz/outcomes from given exposure

can calculate incidence in exposed vs unexposed

minimizes error (prospective)

Question 8

which type of study is good for rare EXPOSURES, fatal diseases

Answer 8

cohort

Question 9

which type of study can calculate incidence among exposed and unexposed

Answer 9

cohort

Question 10

disadvantages of cohort studies

Answer 10

expensive

inefficient for rare disease

long follow up

secular trends may influence behavior/characterstics over time

Question 11

are cohort studies good for rare diseases

Answer 11

NO, good for rare EXPOSURES

Question 12

how are subjects selected for case-control studies

Answer 12

disease status

Question 13

how should cases/controls differ

Answer 13

ONLY IN PAST EXPOSURE

Question 14

can temporality be assessed in case-control studies

Answer 14

no

Question 15

can case-control demonstrate risk indicators or risk factors

Answer 15

indicators only (no temporal relationship)

Question 16

cases and controls must

Answer 16

have had an EQUAL CHANCE OF BEING EXPOSED

Question 17

which type of study is good for rare diseases

Answer 17

case-control

Question 18

advantage of case-control

Answer 18

efficient for rare diseases

good time/money

diseases with long latency period

evaluate multiple exposures

Question 19

can a case control study directly compute incidence of disease in exposed and non-exposed persons

Answer 19

NO

Question 20

disadvantages of case-control

Answer 20

temporal relationship cannot be establishsed

prone to errors in selecting of cases/controls

not optimal for rare exposures

Question 21

cross sectional studies

Answer 21

selection of subjects based on neither exposure or dz status

Question 22

do cross sectional studies need explained etiologic objectives

Answer 22

no

Question 23

advantages of cross sectional

Answer 23

sampling and analytic methods provide for statistically valid inference to populations

exposure and dz are assessed at individual level

Question 24

disadvantage of cross sectional

Answer 24

temporality cannot be assessed

Question 25

what is the primary purpose of randomization in RCT

Answer 25

minimizing of confounding

Question 26

single blinded

Answer 26

participant does not know but investigators do know tx assignment

Question 27

what is information bias

Answer 27

drawing different conclusions depending on their knowledge of which study arm particular participant is in

Question 28

what is selection bias

Answer 28

study recruiters can be eager to recruit “sick persons” into experimental arm

Question 29

meta analysis

Answer 29

combined analysis of data from different studies following strict guidelines